One vertex per element, one color per generator, with an edge from x to x·s.
(1,2)(3,4)(6,9)(10,12)(13,14)(15,22)(16,19)(17,20)(18,21)(23,28)(24,26)(25,27) involution — undirected(5,6,8,9)(7,10,11,12)(13,14,19,16)(15,22,17,20)(18,21,26,24)(23,28,25,27)(2,4)(13,15,19,17)(14,20,16,22)(18,23,26,25)(21,27,24,28)(1,2)(3,4)(5,7,8,11)(6,10,9,12)(13,16,19,14)(15,20,17,22)(18,24,26,21)(23,27,25,28)(13,17,19,15)(14,20,16,22)(18,23,26,25)(21,28,24,27)(13,18,19,26)(14,21,16,24)(15,23,17,25)(20,27,22,28)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.